Hydraulically regulated drive

ABSTRACT

A hydraulic transmission drive comprising a combustion engine, a main pump, and a hydraulic motor, is regulated by adjusting the output of the main pump by regulating means including a hydraulic motor and a regulating pump driven by the combustion engine and driving the regulating motor. An adjustable throttle means is connected with the outlet conduit of the regulating pump and influences the operation of the regulating motor so that when the main pump has an overload, its speed is reduced together with the speed of the combustion engine until the torque of the combustion engine is sufficient.

United States Patent Riedhammer et al.

[ 51 July 25, 1972 [54] HYDRAULICALLY REGULATED DRIVE [72] inventors: Josepf Riedhammer, Horb am Neckar; Fritz-Jorg Glaser, Muehlen am Neckar,

both of Germany [73] Assignee: Brunlnghaus Hydraulik Gmbll, l-lorb (Neckar), Germany [22] Filed: March 3,1970

[21] Appl. No.: 15,987

[30] Foreign Application Priority Data March 4, 1969 Germany ..P 19 10 915.015

[52] U.S- 417/222 [51] Int. Cl... F041) l/26 [58] Fieldoiseal'ch ..4l7/222,218,212,217; 123/ 140.1

[56] References Cited UNITED STATES PATENTS 2,239,882 4/1941 Davis ..60/52 US 2,331,046 10/1943 Robinson ..60/52 US 2,983,101 5/1961 Tyler ..60/52 US 3,302,487 2/1967 Kempson ..60/52 US 2,664,152 12/1953 Davies et al. 417/222 2,038,272 4/1936 Ernst 417/217 2,481,334 9/1949 Nicolls ..60/52 2,664,151 12/1953 Viale 417/222 2,889,780 6/1959 Binford ....417/222 2,445,113 7/1948 Green et al. ..l23/l 40.1

Primary ExaminerWilliam L. Freeh Attorney-Michael S. Striker [57] ABSTRACT Y A hydraulic transmission drive comprising a combustion engine, a main pump, and a hydraulic motor, is regulated by adjusting the output of the main pump by regulating means including a hydraulic motor and a regulating pump driven by the combustion engine and driving the regulating motor. An adjustable throttle means is connected with the outlet conduit of the regulating pump and influences the operation of the regulating motor so that when the main pump has an overload, its speed is reduced together with the speed of the combustion engine until the torque of the combustion engine is sufficient.

10 Claims, 5 Drawing Figures PATENTEDJULZS I972 SHEET 2 0F 2 Fig. 3

HYDRAULICALLY REGULATED DRIVE BACKGROUND OF THE INVENTION The present invention relates to hydraulic regulation of hydrostatic units driven by a combustion engine and having a continuously variable pump volume. The arrangement comprises a regulating pump driven by the combustion engine, and pumping control fluid to the regulating motor by which the volume of the main pump is adjusted.

The regulation serves the purpose to equalize the turning moment of the main pump with the torque produced by the combustion engine which serves as a prime mover. Hydrostatic arrangements of this type including a main pump are widely used in the building construction industry for dredges, winches, and cranes. In such an arrangement, it is necessary to avoid an overloading of the combustion engine which would result in stalling of the same. The combustion engine, usually a Diesel engine, is characterized by a graph showing the turning moment or torque over the number of revolutions. This is a comparatively flat graph which at first rises with the rising number of revolutions until a maximum torque is reached, whereupon the torque gradually drops until the maximum number of revolutions is reached. In the event that the main pump is overloaded, the torque produced by the combustion engine is exceeded so that the rotary speed of the same is reduced. When an extreme overload occurs, the combustion engine stalls.

Regulating apparatus for automatically preventing an overloading of the combustion engine serving as a prime mover of the hydrostatic apparatus, is known.

A centrifugal governor is used by which the piston block of an axial piston pump is adjusted. It is also known to use a centrifugal governor for adjusting a control slide mechanically connected with a regulating motor which adjusts the main pump. This apparatus also requires a great number of mechanical and hydraulic elements, and complicated linkages.

SUMMARY OF THE INVENTION It is one'object of the invention to provide an exclusively hydraulic regulating arrangement for a drive including a combustion engine, a main pump, and hydraulic motor means driven by the main pump.

Another object of the invention is to equalize the turning moment applied to the main pump, with the torque produced by the combustion engine.

Another object of the invention is to use a throttle for influencing the control of the main pump by a regulating motor.

In accordance with the invention, between a regulating pump and a regulating motor acting on the main pump, a control conduit is provided to which a throttle is connected which influences the pressure of the control fluid in the event of an overload, depending on the amount of fluid pumped by the regulating pump.

One embodiment of the invention comprises a main pump including regulating means for continuously varying the pumped volume, a combustion engine for driving the main pump, a regulating pump also driven by the combustion engine and including an outlet conduit, hydraulic regulating motor means connected with the outlet conduit so as to driven by the fluid pumped by the regulating pump, and including movable control means connected with the regulating means of the main pump for adjusting the pumped volume of the same, and throttle means connected with the outlet conduit for influencing, dependent on the amount of fluid pumped by the regulating pump, the pressure of the fluid flowing to the hydraulic regulating motor. As a result, in the event of an overload on the main pump, the speed of the same and of the combustion engine is reduced until the turning moment required by the main pump corresponds to the torque produced by the combustion engine at the reduced speed.

Preferably, the throttle has an inlet connected with the outlet conduit and an outlet for discharging a part of the fluid flowing in the same for influencing the pressure of the fluid flowing to the hydraulic regulating motor.

When the main pump is of the type permitting a reversible delivery, a valve means is provided in the outlet conduit for reversing the direction of movement of the control means of the regulating motor.

In the preferred embodiment of the invention, the throttle means includes a needle valve which can be adjusted to move into and out of a throttle opening. The needle valve is adjusted until the regulating motor has set the main pump to full volume operation at the highest speed of the combustion engine. In this manner, the desired control under overload is obtained.

Instead of once adjusting the needle valve of the throttle, it is also possible to provide a hydraulic arrangement for automatically controlling the needle valve in accordance with the prevailing pressure. In this modification, the outlet of the throttle housing is provided with an auxiliary throttle which produces pressure which is applied to a cylinder chamber in which a piston portion of the needle valve is located so that the needle valve is automatically moved into and out of the throttle opening in accordance with the operational conditions. Preferably, the needle valve is biassed into the cylinder chamber by a spring. This arrangement is particularly advantageous if the combustion engine has a particularly flat torque characteristic since otherwise the graph representing the pressure over the number of revolutions would be very flat.

The present invention provides a simple regulating means which hydraulically adapts the torque taken up by the main pump of a hydrostatic transmission to the torque produced by the combustion engine. The regulation of this operation takes place in accordance with the reduction of the rotary speed of the combustion engine. An advantage of the invention is that the apparatus can be easily adapted to different torque characteristics of difierent combustion engines.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram schematically illustrating a regulated drive according to one embodiment of the invention;

FIG. 2 is a sectional view illustrating a combined regulating pump and throttle according to the embodiment of FIG. 1;

FIG. 3 is a diagram illustrating a modified embodiment of the invention;

FIG. 4 is a sectional view illustrating a combined regulating pump and throttle in accordance with the embodiment of FIG. 3; and

FIG. 5 is a diagram showing the variations of the torque of a combustion engine, and the pressure variation of the regulating pressure depending on the number of revolutions of the combustion engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 3 in which corresponding elements are indicated by the same reference numerals, a combustion engine 1, usually a Diesel engine, drives a regulating pump 2' and a main pump 22 which supplies fluid to a hydraulic motor 22a. The regulating pump 2 has an outlet conduit 2a, 2b connected by a valve 4 with a hydraulic regulating motor 5 which has a movable control means connected with 18, I9 schematically illustrated regulating means 22b of the main pump 22 for adjusting the pumped volume of the same. The main pump 22 is preferably an axial piston pump having a cylinder block and a piston block, the cylinder block being angularly adjustable by the regulating means under the control of the control means 18, 19 of the regulating motor 5. The outlet conduit 2a is connected with a throttle 3 in FIG. 1 and a throttle 3' of somewhat different construction in the arrangement of FIG. 3. Throttles 3 and 3 have outlets l6, and outlet conduit 2a is connected by another outlet 15 and a conduit portion 2b with a slide valve 4 which has three positions. Slide valve 4 connects outlet conduit 20, 2b with the regulating motor 5 which has a control piston 21 20 movable by fluid supplied through slide valve "4, and and loaded by springs 20 21. In the illustrated position, no fluid is supplied by regulating pump '2 through slide valve 4 to regulating motor 5, which means that the motor 5 does not control and regulate the main pump 22 which is in a neutral position..When slide valve 4 is shifted to the lefi as viewed in FIG. 1, the'outlet conduit 2b of the regulating pump 2 isconnected with a chamber in the regulating motor5 and the piston 21 20 is operated in one direction to angularly displace the cylinder block of the axial piston main pump 22 in relation to the piston block so that the displacement volume of the main pump 22 is varied. When control valve .4 is shifted to the right as viewed in the drawing, fluid is supplied from the outlet conduit means 2a, 2b of the regulating pump 2 to another cylinder chamber of regulating motor 5 so that the piston 20 21 moves in the opposite direction, andv adjusts the angular position of the cylinder block of the axial piston main pump 22 in the opposite direction so that the main pump 22 is reversed. Valve 4.con, sequently serves only forvarying the direction in which the main pump 22 pumps the fluid.

The actual construction of the regulating pump 2 and of throttle3 is shown in FIG. 2. The housing a of the regulating pump 2 is directly secured to a housing 10 of the throttle, and the outlet conduit 2a is directly connected with the throttle conduit across-which a throttle wall 11 extends. A frustoconical recess in throttle wall 1] ends in a throttle opening into which the pointed portion of a needle valve 13 projects. The end of the throttle conduitin which the needle valve 13 is located, is connected with outlet 16, while outlet 15, commu-- nicating with the outlet conduit 2a, leads to the outlet conduit portion 2b, as shown in FIG. 1. A thread is provided on needle valve 13 by which its position in relation to the throttle opening 12 canbe adjusted so that the free cross-section of the throttle opening can be varied, as required.

In accordance with the invention, the variable throttle opening 12 of throttle means 3 is adjusted so that at the highest number of revolutions of combustion engine 1, the hydraulicregulatingmotor 5 has turned the tiltable block of the axial piston main pump 22 to its greatest angle and set the main pump 22 to the highest displacement volume. If due to a load of the hydraulic motor 22a driven by the main pump 22, the pressure in the hydrostatic transmission increases, the turning moment required by the main pump 22 also increases. When the turning moment required by the main pump 22 due to'the load of the hydraulic motor 22a driven by the main pump 22, exceeds the output torque of the combustion engine 1, the rotary speed of combustion engine 1 is reduced so that also the volume displaced by the regulating pump 2 drops. Due to the effect of the throttle 3, which operates depending on the amount of fluid supplied to the same, the'pressure in the conduit 2b to the regulating motor 5 also decreases. The

throttle 3 is so designed that the graph Pst representing the pressure drop over the number of revolutions h combustion engine 1, regulating pump 2, and of the main pump 22, is favorable for controlling regulating motor 5.

Thevariation of the pressure is shown as a graph 1, over the number of revolutions n in FIG. 5. The diagram of FIG. 5 also shows a graph representing the variation of the turning moment M over the number of revolutions n of the combustion engine.

When the pressure drops in the outlet conduit 2a, the regulating motor 5 is urged by a spring 21 acting on its control piston 21 20 to move toward the position in which the main pump 22 is in a neutral position, while turning the tiltable block of the axial piston main pump 22 to a smaller angle so that the axial piston main pump 22 requires a smaller turning moment. The reduction of the control pressure takes place until the main pump 22 requires a turning moment which corresponds to the torque produced by combustion engine 1 at the reduced number of revolutions. The regulation is stable in the region of the graph representing the turning moment M; which extends between the maximum number of revolutions of combustion engine 1 and the number of revolutions associated with the maximal torque, which part of the graph is rising. In this manner, a stalling of the combustion engine is reliably prevented.

In the embodiment of FIGS. 1 and 2, the free flow cross-section in throttle opening 12 is adjusted by needle valve 13 only once, and remains then constant during different operational conditions. By varying the free flow cross-section in throttle opening 12 by operation of needle valve 13, an adaptation to the variation pattern of the torque of the combustion engine 1 is possible. Such regulation offers the possibility to protect the combustion engine 1 against an overload, even if in addition to the main pump 22, also other apparatus is driven by the combustion engine 1. In order to protect the combustion engine 1 against an overload, the pressures of the several hydraulic motors 22a driven by the main pump 22 have .to be totalized in accordance with the present invention at the regulator by which the main pump 22 was adjusted and regulated in accordance with the power required by the hydraulic motors driven by the main pump 22. It will be seen that a regulation according to the prior art is substantially more complicated than the apparatus of the invention.

In order to obtain an improved adaptation of the pressure variation represented by graph P, to different torque variation patterns of combustion engines, the modified throttle 3' shown in FIGS?) and 4 is used. Housing 10a of the regulating pump 2 is again combined with the housing 10 of the throttle, and the outlet conduit 2a of regulating pump 2 communicates with a throttle conduit having the inlet 14, and being crossed chamber 8.

The effective surface of the piston of needle valve 13' is I], and the dynamic pressure in conduit 17 and cylinder chamber 8 urges needle valve 13 to reduce the free flow cross-section of the throttle opening 12. By suitably designing the effective surface F, the force of spring 9, and the cross-section of the auxiliary throttle 7, a steep control pressure graph P can be obtained for a particularly flat graph representing the torque It will be understood that each of the elements described above, or two or more together, may also find a useful applica tion in other types of regulating arrangements for hydrostatic transmission drives driven by a prime mover differing from the types described above.

While the invention has been illustrated and described as embodied in a hydraulically regulated drive including a throttle discharging fluid from the output of a regulating pump, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications a without omitting features that, from the standpoint of prior We claim:

1. l-lydraulically regulated drive for a hydraulic motor, comprising a combustion engine; a variable load main hydraulic motor; a main pump driven by said engine to supply pressure fluid to said main hydraulic motor and continuously driving the same so that the turning moment required by said main pump and thereby the speed of said combustion engine vary with variations of the load on said hydraulic main motor, said main pump including regulating means for varying the pumped volume; a regulating pump also driven by said combustion engine and having an outlet conduit; hydraulic regulating motor means connected with said outlet conduit and including control means operated by fluid pumped by said regulating pump, and spring means biasing said control means to a neutral position, said control means being connected with said regulating means of said main pump for adjusting the pumped volume of the latter; and relief throttle means connecting said outlet conduit with a low pressure region, and having a throttle opening substantially adjusted so that at the highest number of revolutions of said combustion engine, said control means of said hydraulic regulating motor means adjusts said regulating means of said main pump to set said main pump to the highest displacement volume, said throttle means reducing in the event of an overload on said main motor and main pump, the fluid pressure in said outlet conduit and in said regulating motor means so thatsaid spring means move said control means toward said neutral position for adjusting said regulating means to adjust said main pump toward a neutral position so that the drive torque required by said main pump is reduced until it corresponds to the torque produced by said combustion engine at the reduced number of revolutions caused by the overload.

2. Hydraulically regulated drive as claimed in claim 1 wherein said throttle means has an inlet connected with said outlet conduit, and an outlet for discharging a part of the fluid flowing in the same for influencing the pressure of the fluid flowing to said hydraulic regulating motor means.

3. Hydraulically regulated drive as claimed in claim 1 wherein said hydraulic regulating motor means includes a hydraulic regulating motor having said movable control means, and a valve means in said outlet conduit for reversing the direction of movement of said control means.

4. Hydraulically regulated drive as claimed in claim 1 wherein said throttle means includes a housing having a throttle conduit with an inlet connected with said outlet conduit and an outlet, a throttle wall across said throttle conduit located between said inlet and outlet of the same and having a throttle opening registering with said throttle conduit, and a needle valve mounted in said housing and having an end portion located in said throttle opening.

5. Hydraulically regulated drive as claimed in claim 4 wherein said housing has another outlet for directly connecting said outlet conduit of said regulating pump upstream of said throttle opening with said hydraulic regulating motor means.

6. Hydraulically regulated drive as claimed in claim 4 wherein said throttle wall has a substantially frusto-conical recess tapering in the direction of the flow of fluid in said throttle conduit and forming at the narrow end thereof said throttle opening; and wherein said needle valve is located on the side of said throttle wall and throttle opening remote from said recess.

7. Hydraulically regulated drive as claimed in claim 4 wherein said housing includes means mounting said needle valve for movement in longitudinal direction thereof into and out of said throttle opening; and means for adjusting the position of said needle valve for varying the size of said throttle opening whereby the amount of fluid flowing from said regulating pump to said hydraulic regulating motor means is adjusted.

8. Hydraulically regulated drive as claimed in claim 4 wherein said throttle means comprises an auxiliary throttle in said outlet located downstream of said throttle opening, a

cylinder chamber in said housing communicating with a portion of said throttle conduit ad acent said auxiliary throttle for receiving pressure fluid, a piston element secured to said needle valve and located in said cylinder chamber, and means biassing said needle valve and piston element into said cylinder chamber so that said needle valve moves into said throttle opening when the pressure of the fluid adjacent said auxiliary throttle and in said cylinder chamber exceeds the force of said biassing means whereby the flow cross section of said throttle opening is automatically adjusted.

9. Hydraulically regulated drive as claimed in claim 8 wherein said needle valve has a pointed front end projecting into said throttle opening, and a thick rear end portion forming said piston element; and wherein said biassing means is a spring abutting said thick rear end portion and a portion of said housing for urging said needle valve into said cylinder chamber.

10. l-iydraulically regulated drive as claimed in claim 8 wherein said housing has an other outlet for directly connecting said outlet conduit of said regulating pump upstream of said throttle opening with said hydraulic regulating motor means. 

1. Hydraulically regulated drive for a hydraulic motor, comprising a combustion engine; a variable load main hydraulic motor; a main pump driven by said engine to supply pressure fluid to said main hydraulic motor and continuously driving the same so that the turning moment required by said main pump and thereby the speed of said combustion engine vary with variations of the load on said hydraulic main motor, said main pump including regulating means for varying the pumped volume; a regulating pump also driven by said combustion engine and having an outlet conduit; hydraulic regulating motor means connected with said outlet conduit and including control means operated by fluid pumped by said regulating pump, and spring means biasing said control means to a neutral position, said control means being connected with said regulating means of said main pump for adjusting the pumped volume of the latter; and relief throttle means connecting said outlet conduit with a low pressure region, and having a throttle opening substantially adjusted so that at the highest number of revolutions of said combustion engine, said control means of said hydraulic regulating motor means adjusts said regulating means of said main pump to set said main pump to the highest displacement volume, said throttle means reducing in the event of an overload on said main motor and main pump, the fluid pressure in said outlet conduit and in said regulating motor means so that said spring means move said control means toward said neutral position for adjusting said regulating means to adjust said main pump toward a neutral position so that the drive torque required by said main pump is reduced until it corresponds to the torque produced by said combustion engine at the reduced number of revolutions caused by the overload.
 2. Hydraulically regulated drive as claimed in claim 1 wherein said throttle means has an inlet connected with said outlet conduit, and an outlet for discharging a pArt of the fluid flowing in the same for influencing the pressure of the fluid flowing to said hydraulic regulating motor means.
 3. Hydraulically regulated drive as claimed in claim 1 wherein said hydraulic regulating motor means includes a hydraulic regulating motor having said movable control means, and a valve means in said outlet conduit for reversing the direction of movement of said control means.
 4. Hydraulically regulated drive as claimed in claim 1 wherein said throttle means includes a housing having a throttle conduit with an inlet connected with said outlet conduit and an outlet, a throttle wall across said throttle conduit located between said inlet and outlet of the same and having a throttle opening registering with said throttle conduit, and a needle valve mounted in said housing and having an end portion located in said throttle opening.
 5. Hydraulically regulated drive as claimed in claim 4 wherein said housing has another outlet for directly connecting said outlet conduit of said regulating pump upstream of said throttle opening with said hydraulic regulating motor means.
 6. Hydraulically regulated drive as claimed in claim 4 wherein said throttle wall has a substantially frusto-conical recess tapering in the direction of the flow of fluid in said throttle conduit and forming at the narrow end thereof said throttle opening; and wherein said needle valve is located on the side of said throttle wall and throttle opening remote from said recess.
 7. Hydraulically regulated drive as claimed in claim 4 wherein said housing includes means mounting said needle valve for movement in longitudinal direction thereof into and out of said throttle opening; and means for adjusting the position of said needle valve for varying the size of said throttle opening whereby the amount of fluid flowing from said regulating pump to said hydraulic regulating motor means is adjusted.
 8. Hydraulically regulated drive as claimed in claim 4 wherein said throttle means comprises an auxiliary throttle in said outlet located downstream of said throttle opening, a cylinder chamber in said housing communicating with a portion of said throttle conduit adjacent said auxiliary throttle for receiving pressure fluid, a piston element secured to said needle valve and located in said cylinder chamber, and means biassing said needle valve and piston element into said cylinder chamber so that said needle valve moves into said throttle opening when the pressure of the fluid adjacent said auxiliary throttle and in said cylinder chamber exceeds the force of said biassing means whereby the flow cross section of said throttle opening is automatically adjusted.
 9. Hydraulically regulated drive as claimed in claim 8 wherein said needle valve has a pointed front end projecting into said throttle opening, and a thick rear end portion forming said piston element; and wherein said biassing means is a spring abutting said thick rear end portion and a portion of said housing for urging said needle valve into said cylinder chamber.
 10. Hydraulically regulated drive as claimed in claim 8 wherein said housing has an other outlet for directly connecting said outlet conduit of said regulating pump upstream of said throttle opening with said hydraulic regulating motor means. 